A. Field of Invention
The present invention relates to wireless communication systems, and more particularly, to a method and system of wireless signal repeating.
B. Description of Related Art
In a typical wireless communication system, an area is divided geographically into a number of cells, each defined by one or more radiation patterns created by an emission of radio frequency (RF) electromagnetic (EM) waves from a respective base transceiver station (BTS) antenna or antenna array. Further, each cell may be divided into a number of sectors, each defined respectively by radiation patterns from directional antenna elements of the cell's BTS. Each sector typically has a beam width of about 120 degrees. However, sectors can have any desired beam width.
For wireless communications, EM signals are not sent through a transmission line, and therefore antennas and/or antenna arrays are required for the transmission and reception of the signals. An antenna array is a set of antennas working together to produce a particular radiation pattern. Each antenna in the array is referred to as an antenna-element (or simply an element).
The radiation pattern of each sector in a cell produces an air interface, which defines a respective coverage area. When a mobile station (MS), such as a cellular telephone, is positioned within such a coverage area of a sector in a cell, the air interface provides a communication path between the MS and the BTS. And the MS can then communicate through this path with entities of the wireless communication system.
Wireless communications from a BTS to an MS are considered to be in a “forward” direction, and therefore such communications are referred to as “forward link” communications. Conversely, wireless communications from an MS to a BTS are considered to be in a “reverse” direction, and therefore such communications are referred to as “reverse link” communications.
Unfortunately, however, both forward and reverse link communications (and other wireless communications) can suffer from varying levels of signal degradation as signals are carried over the air interface between the MS and an antenna of a BTS. For instance, the strength (i.e., power level) of signals transmitted in a forward link direction can diminish substantially as the signals travel over an increased distance to the MS. Further, obstructions such as buildings and foliage can attenuate or otherwise degrade signals passing over the air interface. As a result, forward link signals that arrive at the MS may be too weak to be detected and/or used by the MS, and therefore forward link signals could be undetectable and wireless communications could be blocked or dropped. In addition, the strength of signals transmitted in a reverse link direction can also suffer from similar reductions as the signals travel to the BTS.
One approach that can be used to overcome this difficulty is to increase the power of a signal transmitted by a BTS. A disadvantage with this approach, however, is that the increased power can lead to increased interference in adjacent cells. The power increase can also interfere with other wireless devices in use near the BTS.
Also, this approach does not aid a BTS in receiving a signal transmitted from an MS. Wireless communications are primarily bi-directional communications, in which signals are sent between a BTS and an MS. Therefore, in order to support bi-directional communications, an increase in the transmission power of the BTS would require a corresponding increase in the transmission power of the MS. However, again, an increase in transmission power of the MS could lead to interference with other wireless devices.
Another approach that can be used to increase wireless signal strength is to use wireless signal repeaters. A wireless signal repeater may be able to receive a signal distorted by transmission losses and to regenerate or replicate the signal. Analog repeaters frequently can only amplify the signal while digital repeaters can reconstruct a signal to near its original quality.
For instance, a repeater may be positioned between an MS and a BTS to intercept signals sent between the MS and the BTS. The repeater may amplify the power of these signals and send amplified versions of these signals to the MS or the BTS.
This approach may work in some cases. However, in general not all signals that need to be amplified are intercepted by the repeater. Further, some signals that do not need to be amplified may be amplified, resulting in distorted signals. In addition, existing repeaters lack flexibility in extending coverage to isolated or desired areas. Consequently, a system that overcomes these problems is desirable.